Additive Utility of Peak Expiratory Flow Rate in the Assessment of Chronic Stable Heart Failure Patients

Abstract

STATEMENT OF PROBLEM OR QUESTION (ONE SENTENCE): Does PEFR measurement predict the risk of acute heart failure (HF) exacerbation in patients with chronic Congestive HF evaluated in the outpatient setting? OBJECTIVES OF PROGRAM/INTERVENTION (NO MORE THAN THREE OBJECTIVES): 1) Assess heart failure status in general. 2) Predict risk of acute decompensation of congestive heart failure in stable chronic HF patients. 3) Detect early signs of decompensation, in order to treat early in clinic and minimize the risk for hospitalization and following complications. DESCRIPTION OF PROGRAM/INTERVENTION, INCLUDING ORGANIZATIONAL CONTEXT (E.G. INPATIENT VS. OUTPATIENT, PRACTICE OR COMMUNITY CHARACTERISTICS): The peak expiratory flow rate (PEFR) is the maximal rate that a person can exhale during a short maximal expiratory effort after a full inspiration. PEFR reflects large airway flow, muscular strength and patient effort and is associated with known indicators of HF status. In patients with asthma, the PEFR percent predicted correlates reasonably well with the percent predicted value for the forced expiratory volume in one second (FEV1). Monitoring the PEFR is useful for detecting changes or trends in a patient's asthma control. PEFR is a tool initially used to differentiate dyspnea caused by COPD exacerbation vs Acute Heart Failure. PEFR has been shown to be an effective tool in assessing heart failure (HF) status and its course of recovery in patients with acute decompensated HF. MEASURES OF SUCCESS (DISCUSS QUALITATIVE AND/OR QUANTITATIVE METRICS WHICH WILL BE USED TO EVALUATE PROGRAM/ INTERVENTION): - We prospectively enrolled fifty patients with chronic stable HF, AHA Stage C, NYHA functional class I-III, from our outpatient HF clinic. -Patients with HF hospitalization and those with cardiac surgery ormyocardial infarction within 3 months were excluded. -PEFR was measured for each subject in triplicate. -Averaged PEFR values were compared to predicted averages (adjusted for age, sex, and height) and expressed as percentages. -Data related to patient demographics, hemodynamics, laboratory values, clinical signs and symptoms, and functional capacity were collected. FINDINGS TO DATE (IT IS NOT SUFFICIENT TO STATE FINDINGS WILL BE DISCUSSED): Mean patient age was 69 years old with majority being caucasian males. Majority of patients were NYHA class II/ III, chronic stable heart failure with average duration of 6 years. Majority of the patients had ischemic HF and were noted with reduced ejection fraction. Overall mean percentage of predicted PEFR was 81 %. Subjects with BNP levels above 100 pg/ml had significantly lower PEFR compared to those with BNP less than 100 pg/ml, p = 0.001. PEFR also tended to be lower in patients with positive clinical findings for HF (JVD, lung crackles, edema, ascites) compared to those without clinical findings, p = 0.06. There was no significant difference in PEFR between patients with NYHA class III compared to NYHA class II, p=0.3. KEY LESSONS FOR DISSEMINATION (WHAT CAN OTHERS TAKE AWAY FOR IMPLEMENTATION TO THEIR PRACTICE OR COMMUNITY?): 1) Our study suggests that there is great variability in normalized PEFR ratios even in stable HF patients. 2)We observed relationships of PEFR with key HF biomarkers like BNP but not between NYHA classes. 3) The ease of performance along with its limited cost and portability suggest that the repeated PEFR testing may be an additive simple clinical tool that distinguishes patients with overlapping clinical scenarios (dyspnea of cardiac vs pulmonary origin) and residual risk for adverse HF since it correlates with BNP that is already a key biomarker and prognostic marker in Congestive HF. 4) So far PEFR did not meet objective number (2) and most likely bigger study with bigger population can be initiated to determine that objective.